The present invention relates to an integrated circuit for a time-piece including a plurality of electronic circuits, particularly an oscillator, a frequency divider, electronic means for effecting at least one auxiliary function depending on information delivered to the inputs thereof, a circuit for controlling display means and a circuit for setting the time, the said integrated circuit being provided with a first group of x terminals for connecting the components of the said time-piece external to the said integrated circuit, such as the piezo-electric resonator, the display means and the time-setting means, to corresponding points of the said electronic circuits.
The great majority of electronic time-pieces use quartz oscillators as time base. These oscillators deliver rather high frequency pulses, for example 32 kHz, which are very stable, to a frequency divider which, in turn, drives the circuit controlling display of the time.
The exact frequency setting operations of quartz crystals are long and delicate and noticeably increase the price of these components.
Various systems have been proposed which permit the use of quartz crystals that have not undergone these frequency setting operations, i.e. of quartz, the frequency of which is different from the theoretically necessary frequency.
These systems comprise a circuit adjusting the frequency of the output signals of the divider which acts, as the case may be, by pre-selecting the rate of division of the divider, or by adding or suppressing some pulses at the input of one or more stages of the divider at pre-determined intervals of time.
Whatever the proposed system may be, means must be available to introduce the necessary information for the programming of the adjustment circuit, so that it can act on the divider circuit in such manner that the divider circuit delivers signals at the desired frequency.
One of the simplest means consists in using terminals of the integrated circuit, including all the circuits of the watch, said terminals being reserved for this purpose. By connecting each of these terminals to one pole or the other of the power supply, binary information may be composed that can be used directly by the adjustment circuit. Hence it is possible to introduce with n terminals 2.sup.n separate sets of information. In order to introduce 256 sets of information, it is therefore necessary to reserve 8 terminals. It is known that the terminals of an integrated circuit are a possible source of failure and participate to a not inconsiderable extend in the cost price and dimensions of the integrated circuit. This system, although simple, is therefore not economical.
In order to avoid this large number of terminals, it would be possible to use a ROM memory formed by a combination of interconnections internal to the integrated circuit, selected at the time said circuit is manufactured. Unfortunately, this solution is inflexible for it is necessary to provide as many variants as separate sets of information are desired, 256 with reference to the preceding example.
Another solution resides in using RAM, PROM, REPROM memories and the like. These memories may be programmed at least once by using an addressing circuit within the integrated circuit, thus making it possible to locate the memory position it is desired to programme. Hence, by means of n inputs, it is possible to address and programme 2.sup.n memory positions, enabling 2 (2.sup.n) separate sets of information to be obtained. In order to introduce 256 sets of information, it is therefore necessary to reserve 3 terminals on the integrated circuit. These systems are therefore advantageous from the point of view of the number of supplementary terminals of the circuit, but at present they all have serious disadvantages for application to a watch. The RAM's, for example, lose their information at the moment the power supply is removed, for example, at the moment when the battery of the watch is changed. As to the PROM's and REPROM's, they require either strong currents, or high voltages for programming, a feature which is difficult to obtain in an integrated circuit for a watch, using technology with a low voltage and a weak current.